#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>

int fact(int n)
{
	if (n < 3)
	{
		return 1;
	}
	else
	{
		return fact(n - 1) + fact(n - 2);
	}
}

int main()
{
	int n = 0;
	int fact();
	scanf("%d", &n);
	printf("%d", fact(n));
	return 0;
}